1. PREVENTING CRYPTOGRAPHIC KEY LEAKAGE IN CLOUD VIRTUAL MACHINES STUDENT: FATEMAH ALHARBI PROFESSOR: NAEL ABU-GHAZALEH EE260 SEMINAR IN ELECTRICAL ENGINEERING SPRING 2015 4/23/2015

2. INFORMATION ABOUT THE PAPER Researchers: Erman Pattuk Murat Kantarcioglu Zhiqiang Lin Huseyin Ulusoy The University of Texas at Dallas The 23 rd USENIX Security Symposium 2

3. OUTLINE Defining the problem The proposed solution HERMES Stages Evaluation Conclusion 3

4. Defining the Problem

5. INTRODUCTION TO CROSS-VM SIDE CHANNEL ATTACKS Environment: Cloud Service Providers (CSPs) Advantages: Customers are enabled to outsource their information to the CSPs Disadvantages: Security and privacy Multiple virtual machines (VMs) are placed to the same physical machine Virtual Machine Monitors (VMM) Vulnerable to cross-VM side channel attacks Solution: Virtual Machine Monitors (VMMs) 5

6. VMM IS NOT ENOUGH! Logical isolation among VMs running on the same physical machine Successful attacks: An attacker can place its VMs alongside the victim VMs. Extract ElGamal decryption keys Many others 6

7. The Proposed Solution

8. HERMES Goal: Protect the cryptographic keys in the cloud environment Based on RSA cryptosystem HERMES Stages: 1.Partitioning a private key 2.Bootstrapping the system 3.Establishing connection between a defender VM and a client 4.Renegotiating an inter-VM SSL channel 5.Distributing new shares of the same private keys 8

9. THREAT MODEL Entities: 1.A trusted CSP 2.Defender 3.Adversary Logical isolation: VMM is used Adversary goal: Capture the cryptographic keys 9

10. SETUP The defender holds a set of private RSA keys He/She partitions them over the set of defender’s VMs Each VM holds one share of each partitioned private key The VMs act together to exponentiate with it The defender re-share the keys every t time The shares of a private key in any two sessions are independent Epoch: It is the time window between two consecutive re-sharing moments 10

11. OVERVIEW OF HERMES LAYOUT 11

12. HERMES Stages

13. 1- PARTITIONING KEYS: DISTRIBUTED RSA (D-RSA) MODE Given a private key d Additive Secret Sharing: d is partitioned into k random shares d 1, d 2, …, d k d = d 1 + d 2 + … + d k mod φ(n) http://en.wikipedia.org/wiki/Euler%27s_totient_function The adversary needs to capture all k shares 13

14. 1- PETITIONING KEYS: THRESHOLD RSA (T-RSA) MODE 14

15. 2- BOOTSTRAPPING THE SYSTEM Establish secure SSL channels using the Enhanced SSL protocol: 15

16. 3- CONNECTING TO A CLIENT A client wants to consume the services offered by the defender A defender wants to distribute new shares for the private key 16

17. 4- INTER-VM KEY RENEGOTIATION What will happen if two defender VMs decide to end one SSL session, and renegotiate keys for the next one? Perform a new handshake process using the Enhanced SSL with mutual verification One simultaneous key renegotiation at a given time 17

18. 5- KEY RE-SHARING 1.The defender creates new shares for the same private RSA keys: The shares are independent from the previous ones 2.It connects to each VMs 3.It hands in the new shares for all partitioned private keys When the new share is used? 18

19. Evaluation

20. EXPERIMENTS Case studies: Web server mail server The overhead can be as low as 1% 20

21. Conclusion

22. CONCLUSION HERMES is a novel system to protect cryptographic keys in cloud VMs The key idea is to partition a cryptographic key using additive or Shamir secret sharing With two different case studies, it has been shown that the overhead can be as low as 1% 22